In a mobile communication system of an LTE (Long Term Evolution) scheme, configuration is such that when a mobile station UE communicating in a macro cell detects an entry into a predetermined area corresponding to a CSG (Closed Subscriber Group) cell managed as a fingerprint, the mobile station UE transmits “entering proximity indication” to a radio base station eNB managing the macro cell, and the radio base station eNB that receives the “entering proximity indication” transmits “MeasConfig” to the mobile station UE instructing the measurement of the radio quality in a CSG cell #1 of a frequency F2 in predetermined “measurement gap”.
Furthermore, when the mobile station UE communicating in a macro cell detects an exit from a predetermined area managed as a fingerprint, the mobile station UE is configured to transmit “leaving proximity indication” to a radio base station eNB managing the macro cell, and the radio base station eNB that receives the “leaving proximity indication” is configured to transmit “MeasConfig” to the mobile station UE instructing an interruption of the measurement of the radio quality in a CSG cell #1 of a frequency F2 in predetermined “measurement gap”.
Here, a CSG cell indicates a cell that can be accessed only by a particular mobile station UE, wherein the mobile station UE checks the broadcast information of each cell, and if the CSG ID included in the broadcast information is included in “allowed CSG list” stored in the mobile station UE, the mobile station UE determines that the mobile station UE belongs to the CSG, and if the same is not included, the mobile station UE determines that the mobile station UE does not belong to the CSG.
Furthermore, when “CSG indication” included in the broadcast information is “TRUE”, only the mobile station UE belonging to the CSG becomes able to access, and when the “CSG indication” included in the broadcast information is “FALSE”, the mobile station UE belonging to the CSG is given preferential access.
However, in the above-described mobile communication system, because the conditions for the transmission of the “entering proximity indication” and the “leaving proximity indication” by the mobile station UE are not stipulated clearly, the “entering proximity indication” or the “leaving proximity indication” is transmitted frequently by the mobile station UE, which may result in wastage of radio resources.